Former US president Jimmy Carter has urged his country and China, two of the world's biggest fossil fuel polluters, to take the lead on halting climate change.

If the two economic and political giants could agree on a way forward, the rest of the world would likely follow their lead, the statesman said on Tuesday on the sidelines of a climate change discussion at the Paris Institute of Political Science.

"If we could put those two together as leaders of the Western world and the developing world and get them to agree on almost any formula for long-term and effective correction of the deterioration of the environment ... I think the other countries would follow their leadership," Carter said.

He said he had encouraged President Xi Jinping along these lines, and had had discussions with US Secretary of State John Kerry.

Carter took part in the Paris meeting on Earth Day as a representative of The Elders, a grouping of global leaders brought together by Nelson Mandela in 2007 to promote peace, justice and human rights.

He told the students that climate change threatened world peace.

"If we don't address the global warming issue, we are going to see rapidly increasing conflict around the world.

"As people grow more desperate for food, for clean air and water, there is going to be increasing violence within countries and between countries."

The next 18 months would be crucial to determine the success of efforts to halt global warming "or catastrophic failure", said the Nobel Peace laureate.

The UN is seeking to hold warming to two degrees Celsius, at which scientists believe we can still avoid the worst effects of climate change.

UN Secretary General Ban Ki-moon will host heads of state and government in New York in September to "catalyse action" ahead of a meeting in Paris at the end of next year where the world's nations are due to sign a global climate pact.

The deal, which must come into operation by 2020, should outline emission curb targets, which have the topic of years of often belligerent talks.

Negotiators will gather again in Lima, Peru in December to come up with an outline for the agreement.

Carter said he hoped "as many of the world's leaders as possible" would attend the September meeting with Ban.

"Everyone who is interested in the subject needs to marshal our efforts now to make sure we do not fail in Paris in 2015."

Carter described climate change as "the greatest challenge the human race has ever faced".

This article appeared in the South China Morning Post print edition as US, China urged to take lead on climate change